Riser drilling system with controlled deflection gimbal joints



Aug.-11, 1970 c. E. NOLAN, JR" ET AL 3,523,578

RISER DRILLING SYSTEM WITH CONTROLLED DEFLECTION GIMBAL JOINTS Filed May16, 1968 4 Sheets-Sheet 1 P0552 TL. C /,0

ywzmwmg u ATTORNEYS Aug. 11, 1970 c. E. NOLAN, JR ET AL 3,523,578

RISER DRILLING SYSTEM WITH CONTROLLED DEFLECTION GIMBAL JOINTS Filed May1 1968 4 Sheets-Sheet 2 5&9 F4 008 INVENTORS C2 v05 5. A/044/14T/fiATTORNEYS Aug. 11 1970 c N, JR ET AL 3,523,578

RISER DRILLING SYSTEM WITH CONTROLLED DEFLESTION GIMBAL JOINTS Filed May16, 1968 4 Sheets-Sheet 3 /0 2 2a. 204 2/2 2/6 2/4 /6 4 2/6 Z/ /6 ZINVENTORS C1. YDEE-NDL fl/Vx/A.

Po BEL/=77 L-cPfl/A/ ATTORNEYS Aug. 11, 1970 c. E. NOLAN, JR, ET AL3,523,578

RISER DRILLING SYSTEM WITH CONTROLLED DEFLECTION GIMBAL JOINTS Filed Mayis, 1962; 4 Sheets-Sheet 4 INVENTORS CL r055 A OLW/V, JR

P055921 .CZwv/y ATTORNEYS United States Patent 3,523,578 RISER DRILLINGSYSTEM WITH CONTROLLED DEFLECTION GIMBAL JOINTS Clyde E. Nolan, Jr., andRobert L. Crain, Houston, Tex., assignors to Gray Tool Company, Houston,Tex., a corporation of Texas Filed May 16, 1968, Ser. No. 729,716 Int.Cl. E21b 43/00; E21c 19/00 U.S. Cl. 165-5 13 Claims ABSTRACT OF THEDISCLOSURE The foregoing abstract is not intended to be a comprehensivediscussion of all of the principles, possible modes or applications ofthe invention disclosed in this document and should not be used tointerpret the scope of the claims which appear at the end of thisspecification.

BACKGROUND OF THE INVENTION Offshore drilling of petroleum Wells isusually conducted from a stable platform such as a platform fixedlysupported from the ocean floor or a floating platform, for

instance on a barge or ship. Especially in the case of floatingplatforms, it is desirable to drill the well with blowout preventersmounted near the ocean floor and to communicate the well to the rigduring drilling via a marine riser, a universal joint and slip joint. Itis conventional to place one or more remotely disconnectable connectorsin such riser systems. Accordingly, the preventers and wellhead areprotected against damage should wind and wave action move the drillingvessel from location or disturb the position of the stable platform fromwhich drilling is being conducted.

Of the universal joints which have been previously proposed for use insuch marine riser systems, ball joints and flexible pipe sections havepredominated. One drawback of many ball joints is that the ball and itssocket provide both primary sealing and primary support at the samesurface locations on the respective elements. Thus excessive wear andseal disruption may occur at these surfaces. Flexible pipe sections,especially those which include interlocked stacks of annuli of compositemetal and rubber elements, also wear excessively and may snake duringuse, sufficiently to cause equipment to become stuck in the well ordamaged due to intricate bending that such equipment cannot tolerate.

A discussion of certain problems encountered in drilling from a floatingvessel is provided in the U.S. patent of Postlewaite et al. 3,313,358.

SUMMARY OF THE INVENTION The present invention provides a riser drillingsystem including at least one gimbal joint and preferably a plurality ofthem spaced along the riser to even out deflection. The gimbal joint ofthe invention includes load cell means for controlling the gimbal jointdeflection. The gimbal joint primary load transmission does not involvethe primary sealing surfaces thereof. When a plurality of such gimbaljoints are axially spaced in a riser, a curved beam is simulated byallowing relative angular movement between the casing joints withoutcausing or depending upon flexure of the casin=g.1When the riser systemis maintained in tension from support at the platform, the restorationforce provided by the load cell means at the gimbal joints tends tocorrect reversal of pipe angle, i.e. snaking (the situation depicted inthe U.S. patent of McNeill 2,606,003).

One of the gimbal joints is preferably located just above the blowoutpreventer stack near the ocean floor. A telescoping joint to provide forvertical motion of the platform is preferably included in the systemwhen the platform is a floating or mobile one.

Objects of the invention thus include providing for lateral movement ofthe drilling platform while minimizing excessive wear and side loading;and, while facilitating retention of control, allowing circulation ofmud, fluids and cuttings, and guidance for running, connection anddisconnection of wellhead parts, tools and conduits.

The principles of the invention will be further hereinafter discussedwith reference to the drawings wherein a preferred embodiment is shown.The specifics illustrated in the drawings are intended to exemplify,rather than lim it, aspects of the invention as defined in the claims.Specifically, it should be borne in mind that the gimbal systemdisclosed could be advantageously used in other environments, forinstance chemical process plant fluid-tight piping systems, where pipemisalignments during transport of fluid under pressure must be dealtwith.

In the drawings:

FIG. 1 is an overall elevation view of apparatus of the invention inoperating position;

FIG. 2 is a fragmentary elevation view of part of the apparatus of FIG.1 showing controlled deflection thereof and FIG. 2a is a view of adetail thereof on larger scale;

FIG. 3 is an elevation view, with one quadrant cut away and sectioned,of a controlled deflection gimbal joint according to the preferredembodiment of the invention; and

FIG. 4 is an exploded perspective View of the gimbal joint of FIG. 3.

DESCRIPTION OF THE PREFERRED EMBODIMENT A drilling system 10 is shown inFIG. 1 including a marine vessel 12 at the suface of a body of water 14such as an ocean or gulf. The vessel 12 is provided with a well 16through which drilling operations are conducted. The vessel also hasanchor line provisions 18 for mooring the vessel on location. Other,similar vessels have drilling platforms cantilevered over the side ofthe vessel and/ or have legs which may be lowered to the bottom toprovide stable support. Other similar vessels are kept on location viaautomatic positioning systems which do not require mooring of thevessel. Any of these may be used in place of the vessel 12 shown. Oncethe drilling vessel has been properly located, drilling operations maybegin. In the typical operation shown already underway in the drawing, atemplate or landing mat 20 loaded with ballast has been lowered tosupport on the ocean floor 22. A drill string having an appropriatelowering tool may be used to lower the mat 20. Guide lines (not shown)may lead from the mat 20 to the rig to assist in the lowering of theguide base or landing base.

The landing mat 20 has a central, vertical bore 24 provided at its upperextent with a coaxial, annular, upwardly concave, spherically curvedseat 26.

A hole is then drilled down through the template into the ocean bottomfor installation of the conductor pipe. At this stage, noenvironment-excluding conduit need extend to the surface. Water may bepumped down through the drill string to assist in washing material fromthe 3 hole being drilled, with returns spilling out at the ocean floor.

A guide base or landing base 28 is next secured around the guidelinesleading down to the landing mat using a guide frame (not shown) andlowered to support on the landing mat, for instance on a drill string.Once the guide base has landed, the guidelines leading from the landingmat may be retrieved.

The landing base 28 includes a short length of large diameter pipe 30open at the lower end and topped by an integral, radially outwardlydirected flange 32. A circumferential, radially outwardly extendingframe 34 is secured to the pipe 30 intermediate its ends. A plurality,for instance four, guide posts 36 project upwardly from the frame 34 andinclude releasable connections for guidelines 38 which extend to thesurface.

At its lower extent the frame 34 has a coaxial, annular downwardlyconvex, spherically curved seat 40, for instance provided by the loweredges of a plurality of equiangularly spaced, radiating, longitudinallyextending plates 42. The seat 40 cooperates with the landing mat seat 26in ball and socket fashion, mounting the landing base on the landingmat.

Some of the components subsequently lowered to the bottom or retrivedtherefrom may be guided in transit by being provided with a conventionalwraparound guide frame which runs along the guidelines 38. When use ofthe guide frame is completed it is unlatched and pulled free. Duringrunning and retrieving, the guidelines 38 are maintained under tension,for instance by their being secured to conventional constant tensionwinch arrangements 44 mounted in the vessel well 16 below the rotarytable 46.

In order to accommodate the landing base 28 to the particular type ofend connections shown in the drawing, an axially short cross-over sub 48is shown secured on the upper end of the landing base. The sub 48 has aradial flange S at its lower ends, by which it is bolted at 52 to flange32. At its upper end, the sub 48 is provided with an enlarged flange 54,having an annular, external frustoconical clamp receiving wedgingsurface 56; an annular, internal, inwardly flaring frustoconical sealingsurface 58 and an axially presented upper end surface. (A similar flangeis described in greater detail in the U.S. patent of Watts et al.2,766,999 in respect to FIG. 1 thereof.) The connection at 32, 50, 52 isperformed at the surface, prior to lowering of the landing base 28. Thesub 48 and connection at 32, 50, 52 may be wholly dispensed with byintegrally providing the flange 54 directly on the upper end of the pipe30.

If desired, the conductor pipe and first casing head may be run in aseparate step, after the landing base, including its upper flange 54,have been landed. However, this requires the use of an additionalremotely disconnectable connector to secure the first casing head to thelanding base upper flange. As the first casing head remains in place,once landed, this would result in the permanent tying-up of a relativelyexpensive piece of equipment. Accordingly, the following alternative ispreferred: prior to lowering of the landing base 28, a conductor housingor first casing head 60, with the conductor pipe 62 depending therefrom,is mounted on the landing base 28 at the landing base upper flange 54.

The first casing head 60 is substantially the same as the casing head100 shown in the U.S. Patent of Grain et al. 3,287,030, which describesthe structure thereof in greater detail. First casing heads of otherdesign could be used in the present instance. Suflice it to say, thatthe casing head 60 is generally tubular having a bore 64 communicatingwith the bore 66 of the conductor pipe 62 which depends from the lowerend thereof. The upper end of the conductor pipe may be secured to theconductor housing or first hanger 60 in any suitable fashion, such aswelding, threading or the like, as is common in the industry.

The bore of the first casing head 60 includes at least one casing hangerseat 68, and a hanger-to-head latching groove 70. The exterior of thefirst casing head 60, midway along the length thereof, is provided withan external circumferential rib 72, approximately equal in diameter tothe OD. of the flange 54. The rib 72 has a radially directed, axiallyfacing lower surface 74 and a frustoconical axially facing, clampwedging upper surface 76. As shown preassembled, the rib surface 74abuts the flange 54 upper surface and an expansible-eontractile clamp 78holds the two secured together. The clamp 78 is of the type shown inFigures 97-B or 109 on pages 2099 and 2105 of the Composite Catalog ofOil Field Equipment and Services; 1966-1967 edition; Gulf PublishingCo.; Houston, Tex., U.S.A.; and further described in the aforementionedU.S. Patent of Watts et al.

The head 60 extends generally cylindrically upwardly from the rib 72,terminating in an enlarged flange 80, which is similar to the flange 54,in that it includes an interior flared sealing surface, a flat endsurface and an exterior flared clamp wedging surface. An enlarged,exterior cylindrical surface portion 81 on the head 60 just below itsupper end acts as a guide for the remotely operable connector slidingpiston, as will become more apparent hereinafter.

Once the guide base, conductor pipe, first casing head and hanger havebeen landed as a unit, for instance on a drill string, and the guidelines 38 connected, the conductor casing may be cemented in conventionalfashion by forcing cement down the drill pipe, out through the lower endof the conductor pipe and up the annulus between the conductor pipe andthe hole in the ocean floor.

In order that drilling of the remainder of the well may begin, themarine riser 82 is now installed. In general, the marine riser is madeup at the surface, bottom to top, with appropriate checking of seats andseals and installation of hydraulic, mechanical and other control linescompleted in sequence as will be apparent to those familiar withunderwater drilling.

With reference to FIGS. 1 and 2, the marine riser, from the bottom up,in the example shown, includes a first remotely connectable anddisconnectable connector 84. The one shown is depicted and discussed ingreater detail on page 2106 of the 1966-1967 edition of the CompositeCatalog. Other remotely operable connectors could be used. Suffice it tosay that, in the example shown, mechanical and/ or hydraulic actuationof the piston 86 slides the clamp segments 88 radially into (shown) andout of (not shown) clamping engagement of the flanges and 90. The flange90 on the connector interiorly mounts a flexi =ble lip seal ring 92, forinstance as shown in FIGS. 1 and 4-6 of the U.S. patent of Watts et al.,3,231,297.

A conventional blowout preventer stack is shown, somewhat schematically,at 94.

Although requirements vary depending upon pressures expected to beencountered and drilling and completion procedures to be followed, atypical blowout preventer stack might include one or more ram-typepreventers 96 provided with pipe and blind rams, surmounted by a bagtype preventer 98. The stack may be an integrated structure includingsupporting and guiding framework members and control line connections.The stack 94 shown includes upper and lower tubular sections 102, 100,termimating in clamp and sealing ring receiver flanges 106, 104 whichreceive seal rings 110, 108 and clamps 114, 112, for instance as inWatts et al. 2,766,999. The clamp 112 mounts the stack 94 on theremotely disconnectable connector 84; the clamp 114 is shown mounting atubular extension sub 116 on the stack tubular section 102. Theextension sub 116 includes a clamp and sealing ring receiving flange 118at its lower end, another one, 120, at its upper end and a pistonguiding enlarged exterior cylindrical surface 122 intermediate its ends,similar to the surface 81 on the first casing head 60. The extension sub116 could be made integral with the stack tubular section 102, thuseliminating the joint at 118, 114, 106, 110.

The remainder of the marine riser shown includes, from the bottom, asecond remotely operable connector 124, a first gimbal joint 126constructed in accordance with the present invention and depicted ingreater detail in FIGS. 3 and 4, along segment 128 of marine riserconduit, consisting for instance of several joints thereof, a secondnovel gimbal joint 130, a second long segment 132 of marine riserconduit, a third novel gimbal joint 134, and the remaining segment 136of riser, preferably having a conventional vertical motion permitting,telescoping joint 138 and a bell nipple 140 at the upper end thereofwith connection provisions 142 at the vessel well for retaining aconstant tension on the marine riser.

The novel gimbal joints 126, 130 and 134 will now be described ingreater detail with reference to FIGS. 3 and 4. Since the joints 126,130 and 134 are alike, the joint 126 will be used as an example.

The gimbal joint 126 includes a centrally located, tubu lar gimbal sealmounting ring 142, shown having its thickest section midway along theaxial' length thereof. A circumferential rib 144 is formed on the ring142, exteriorly thereof, at the thickest section. From this section thering thickness gradually decreases in both axial direc tions, bothinteriorly and exteriorly. Accordingly, when the gimbal seal ring 142tilts during use, to the permitted degree of tilting, the effectivediameter of its through bore 143 remains substantially the same,minimizing any tendency for equipment to hang or bind within the gimbalseal ring through bore.

Annular sealing rings 146, 148 of resilient long wearing, marineresistant sealing material such as neoprene are recessed in the radiallyinner corners of the ends of the gimbal seal ring 142 so as to extendslightly axially beyond (for instance, Ma inch beyond) flushness withthe adjacent radially outer corners of the gimbal seal ring. The gimbalseal ring outer corner axial end surfaces and annular sealing ring 146,148 axial outer end surfaces are spherically, convexly curved about apoint P lying at the geometric center of the gimbal seal ring 142. Thus,the gimbal seal ring outer corner axial end surfaces engage the seats168 to transmit some of the load between these members, causing thetrunnions 192 to be loaded as simple beams instead of as cantileverbeams. The load carried by the gimbal seal ring 142 does not causevertical movement of the ring due to transfer of the load to theopposing two trunnions, and because of its low magnitude, the load onthe gimbal seal ring does not distort the gimbal seal ring.

At four equiangularly spaced points about the ring 142, radiallyoutwardly opening cylindrical sockets 150, 152, 154, 156 are formedtherein through the rib 144, but terminating short of the bore 143. Thelongitudinal axes of these sockets intersect at the geometric center Pof the gimbal seal ring 142.

The gimbal joint 126 further includes two end connector elements 15-8,160 which are substantially identical in structure, excepting that theupper one, 160, is inverted and rotated 90 degrees about thelongitudinal axis thereof, from the lower one, 158, in assembling thegimbal joint 126. The lower end connector element will be furtherdescribed by way of example.

The lower end connector element 158 is generally tubular having anexterior which gently flares toward the flat, axially facing, axiallyinner end thereof 1-61. The axially outer end of the element 158 isprovided with means for securing it to an aligned conduit end, forinstance the end of a marine riser pipe end flange. Where the connectionis to be made using contractile-expansible clamps as described in theaforementioned Watts etal. US. patent 2,766,999, the securing means onthe element 158 lower end may comprise a flange 162 provided with anexterior clamp wedging surface 164 as shown.

Toward its outer end, the through bore 166 of the element 158 isgenerally cylindrical, merging axially inwardly with a coaxial, annular,spherically, concavely curved seat 168 which flares toward the end 161.The seat surface 168 is curved about the point P and has a radius, fromthe point P (when assembled, FIG. 4), that is, slightly greater thanthat of the gimbal seal ring outer corner axial end surfaces andslightly smaller than that of the gimbal seal ring 142 sealing rings146, 148 axially outer end surfaces. Its length of arc, in the senseparallel to the longitudinal axis of the element 158 is about 30degrees. 1

The element 158 is completed by two massive ears 170, 172 shown secured,for instance by welding, to diametrically opposed regions on theexterior of the element and extending axially beyond the inner endthereof. The ears 170, 172 could be integrally formed on the element158. Aligned cylindrical holes 174, 176 are formed through the ears 170,172 along a diametral line which passes through the point P.

The direct distance between the facing inner surfaces of the two ears170, 172 is at least slightly greater than the outer diameter of thegimbal seal ring rib 144 in order to prevent interference duringoperation of the gimbal joint.

The gimbal joint 126 further includes a gimbal ring or trunnion mountring 178 which, in the example shown, is generally tubular and ofapproximately the same axial extent as the gimbal seal ring. Thetrunnion mount ring 178 has an inner diameter which is larger than thedirect diametral distance between corresponding points on the exteriorof the four ears 170, 172.

At four equiangularly spaced joints radially directed openings 180, 182,184 and 186 are formed centrally therethrough on radii which intersectat the point P. Peripherally adjacent the openings -186, flats 188 areformed on the exterior of the trunnion support ring 178. A plurality ofsmall threaded openings 190, for instance three, are shown surroundingeach opening 180-186, opening through respective flats 188.

In assembling the gimbal joint, the gimbal seal ring 142 is placed onthe lower end connector element 158 sealing surface 168 so that thegimbal seal ring sockets 150 and 154 are axially aligned with theopenings 174, 176 through the ears 170, 172 of the lower end connectorelement.

The upper end connector element 158, inverted and in the orientationshown in FIG. 3 is lowered onto the gimbal seal ring so that the gimbalseal ring sockets 152 and 156 are axially aligned with the openings 174,176 through the ears 170, 172 of the upper end connector element and theaxially upper end of the gimbal seal ring engages the upper endconnector seat 168. The gimbal ring or trunnion mount ring 178 islowered to a girth encircling position respecting the subassembly justdescribed. The openings 180, 182, 184, 186 of the gimbal ring ortrunnion mount ring 178 are respectively axially aligned with the gimbalseal ring sockets 150, 152, 154, 156.

The gimbal joint 126 further comprises four gimbal pins or trunnions192, each comprising a generally cylindrical axle portion 194 and amounting means 196 shown comprising a threaded socket in the outer endof the axle portion, a circular plate 198 having a central and severalangularly spaced radially intermediate openings 199 therethrough. A bolt200 received through the central opening and threaded into the axleportion socket secures the plate to the axle portion. The gimbal pininner ends are inserted through respective openings 180, 182, 184, 186and then through respective openings 174, 176 of the upper and lower endconnector elements, and into the respective sockets 150, 152, 154, 156.Bolts 202 are then threaded through the openings 199 into the threadedopenings on the trunnion support ring. This secures the trunnions orgimbal pins to the trunnion mount ring or gimbal ring; journals theupper end connector element for pivotal movement with respect to thetrunnion mount ring about the axis of the two trunnions which supportit; journals the trunnion mount ring for pivotal movement with respectto the lower end connector element about the axis of the two trunnionsconnecting these elements; and supports the gimbal seal ring 142 withinthe joint in sealing engagement with the upper and lower end connectorelement spherically curved sealing surfaces 168.

A particularly important feature of the gimbal joint 126 will now bedescribed. It should be apparent that, were the gimbal joint 126 toconsist only of the parts so far described, it would have nopredisposition to assume or maintain a condition wherein the upper andlower end connector elements were axially aligned. Furthermore, ifdeflected from axial alignment, little or no restorative force would bepresent to return the joint to an axially aligned condition. Inaddition, if several of such joints were interspersed in a marine riserpipe, the pipe could assume a snaked condition wherein each of thejoints was bent toward a different azimuth.

In underwater well drilling, this state of affairs would be highlyundesirable, since well drilling or completion parts disposed within theriser could become stuck therein, tubular parts could hang and twist offand, in any event, excessive wear of the parts and of the riser could beexpected.

In order to prevent such undesirable occurrences, the gimbal joint ofthe invention is provided with means tending to predispose it in anangularly aligned condition and tending to restore it to an angularlyaligned condition, if deflected therefrom.

In the embodiment shown, these predisposing and restoring means comprisea plurality of load cells 204, 206 respectively mounted between thelower end connector element and the gimbal ring, and between the upperend connector element and the gimbal ring. Although arrangementmodifications are possible, the presently preferred embodiment providestwo load cells 204 diametrically opposite one another midway between theears 170, 172 of the lower end connector and two load cells 206diametrically opposite one another midway between the ears 170, 172 ofthe upper end connector. The load cells 204 and 206 are all ofsubstantially identical construction and may, for instance, comprise adouble-acting steel coil spring 208 having a force constant of 6,000 to7,200 pounds per foot, and an unstressed length of about 10 inches.

The spring is received within a capsule consisting of opposed cup-shapedsections 210, 212. The capsule section 210 is of smaller O.D. than theID. of the section 212 and the former is partly received within thelatter. The ends of the spring are fixedly mounted in the respectivesections 210, 212. A U-shaped annular, flexible rubber diaphragm havingopposite ends thereof sealingly connected to the facing, overlappingsurfaces of the sections 210 and 212 excludes the marine environmentfrom the spring. Suitable means, such as eyes 214 on the section 210,212 outer ends, the gimbal ring, and the upper and lower end connectorelements, together with nut and bolt assemblies 216 through the eyes,mount the load cells on the gimbal joint.

In the construction shown, the load cells extend between the exterior ofthe respective end connector elements and the nearest axial ends of thegimbal ring, forming approximately 30 degree angles with thelongitudinal axis of the gimbal joint, when the gimbal joint is in anaxially aligned condition.

Upon angular tilting of the gimbal ring about the trunnions pinning itto the lower end connector element, one of the load cells 204 will becompressed and the other will be extended under tension. The restorativeforce provided by both in a sense to return to an unstressed conditionwill tend to return the gimbal ring to the datum position shown in FIG.4.

Upon angular tilting of the upper end connector element about thetrunnions pinning it to the gimbal ring one of the load cells 206 willbe compressed and the other will be extended under tension. For thejoint as a whole, the restorative force is substantially proportional tothe degree of tilt of the upper end element with respect to the lowerend element irrespective of the azimuth.

It should be apparent that more similar load cells could be provided,angularly spaced about the joint. Also, it should be apparent that theload cells need not comprise a coil spring or an encapsulated coilspring, but could, for instance, comprise hydraulic pneumatic and/ormechanical equivalents thereof. An example of a commercially availabledevice which could be used as load cells 204 and 206 is a compressionloaded liquid spring available from Taylor Devices, Inc., New York, oras shown in the US. patent of Taylor, 3,256,005.

The load cells need not be of a type having a zero restorative forcenull position from which they can be disturbed by extension orcompression of the restorative force providing element. In fact, in someapplications, such a device would he undesirable since it would berelatively dead at and near its null position. Instead, the load cellsmay be provided with pretensioned or precompressed restorative forceproviding elements, respective ones of which counterbalance one anotherabout the joint.

As another alternative one or more precompressed load cells may befixedly mounted, via one end, on either the trunnion mount ring 178 oran end connector element 158 or 160 having its free end positioned tobear against the adjacent element 178, 158 or 160 to which it is notattached. Thus such load cells operate in compression only, since theadjacent element, if displaced further, merely moves free of theparticular load cell free end after the load cell has recovered to itspreloaded state.

In the embodiment shown, the maximum possible tilt of the upper endconnector element with respect to the lower end connector element isabout four degrees, at which point the axial end surfaces of the rib144, of the seal mounting ring 142, contacts the exterior face 161 ofthe end connector element 158. Such contact does not cause any load tobe transmitted to the seal ring seat surface 168 or the seal ring seals146, 148. As it is, within the allowed degree of tilting or at maximumdeflection, the seals 146, 148 are always in annular, resilient sealingcontact with the sealing surface 168 regardless of the degree or azimuthof allowed tilting. Furthermore, it should be apparent that when thejoint 126 is incorporated in a string of heavy pipe, the weight of theportion of the string which is above the joint and the effect of anytensile strain pulled on the string from above, substantially bypass theseals at 146, 168 and 148, 168 and are transmitted between the two endconnector elements via the gimbal ring, trunnions and seal ring 142without any relative movement to cause the seal ring 142 to engage thespherical seats 168.

Another feature of the joint 126 is Worthy of note; inasmuch as theseals at 146, 148 are at all times circumferentially surrounded by anouter portion of the respective end connector element adjacent its end160, fluid pressure within the joint tends to push the seals intotighter sealing contact with the seats 168. Thus, the embodiment shownin FIG. 4, when in use in an underwater drilling system is enabled towithstand an internal fluid pressure of at least about 200-300 p.s.i.However, apparatus constructed in accordance with the principles of theinvention may be used in industrial applications in process equipmentunder nearly static conditions feasibly reaching several thousand poundsper square inch of pressure.

Returning to FIGS. 1 and 2, axially spaced incorporation of several, forinstance three, of the novel gimbal joints in the marine riser at forinstance 40 to foot intervals preferably starting immediately above thepreventer stack spreads the necessary angular deflection out over thelength of the riser and maintains the diameter of the bore of the riser,minimizing chances that well drilling or completion parts will hang orbecome struck in a bend.,

Furthermore, since the load cells of all of the novel gimbal joints maybe provided with equal restoring forces, if desired, the longer momentarm to which the lowest gimbal joint is subject will cause fulldeflection therebefore the next upper gimbal joint deflects, etc. up tothe uppermost joint. Deflection is thus controlled and snakingprevented.

Once the riser has been installed as described, further well drillingand completion operations may be conducted through the riser, forinstance as more completely described in the abovementioned Crain et al.US. Pat. 3,287,030 and/or as described in the US. patents of Hynes3,289,765 and 3,336,978. This may include lowering a drill string downthrough the riser bore, drilling hole for the next inner casing string220, and lowering the casing string 220 with its hanger 222 to supportwithin the casing head 60. (The particular hanger 222 shown in FIG. 1 isshown in more detail in the abovementioned Crain et al. US. patent.)

If during drilling and/or completion it should for some reason becomenecessary or desirable to separate the marine riser and remove orreplace segments thereof, this may be done by manipulation of theremotely disconnectable connectors, described above. For instance,although one set of blowout preventers may be used throughout thedrilling and completion of the well shown in FIG. 1, some operators maywish to initially use a large bore, lower pressure rated unit, thenswitch to a smaller bore, higher pressure rated unit when drilling holefor the oil string of casing.

Once drilling is finished the well may be completed, or temporarily orpermanently abandoned as is known in the art. At such stage, the marineriser, including the blowout preventers, is detached from the well andretrieved for reuse.

The novel gimbal joints described herein, except for the resilient sealrings described above, are preferably made of A151 4140 steel. If neededfor corrosion or environmental protection, working surfaces of thegimbal joints may be coated with standard protective coatings, such aselectroless nickel coatings.

More or less than three of the novel gimbal joints could beadvantageously used in the riser, and in instances where only one isemployed, for instance just above the BOP stack, inclusion of the loadcells on the joint is not essen tial in some instances, as will beapparent.

It should now be apparent that the riser drilling system with controlleddeflection gimbal joints as described hereinabove possesses each of theattributes set forth in the specification under the heading Summary ofthe Invention hereinabove. Because the riser drilling system withcontrolled deflection gimbal joints of the invention can be modified tosome extent without departing from the principles of the invention asthey have been outlined and explained in this specification, the presentinvention should be understood as encompassing all such modifications asare within the spirit and scope of the following claims.

What is claimed is:

1. In a tubular joint having two axially alignable pivotallyinterconnected tubular conduit elements and including means sealinglyinterconnecting the through bores of the two tubular conduit elements,the improvement comprising: a support member positioned adjacent thepivotal interconnection of the tubular conduit elements; at least onefirst load cell having an end thereof secured to one of the tubularconduit elements and an opposite end thereof connected to the supportmember; at least one second load cell having an end thereof secured toone of the tubular conduit elements and an opposite end thereofconnected to the support member; each load cell including means forexerting an axial alignment restoring force between the support memberand the respective tubular conduit element in proportion to thedeflection of the respective tubular conduit element from axialalignment with the support member.

2. A gimbal joint for a fluid conduit, said gimbal joint comprising: afirst tubular element having a longitudinal through bore; a secondtubular element having a longitudinal throughbore; means defining anannular, coaxial, concave, spherically curved sealing surface on each ofsaid tubular elements, within the throughbore thereof, adjacent andenlarging toward one end of respective tubular elements; a gimbal ringdisposed circumferentially of said joint adjacent said tubular elementone ends; first gimbal pin means on said gimbal ring, proceedingradially thereof from two diametrically opposed locations on said gimbalring; said first gimbal pin means pivotally mounting said first tubularelement at two diametrically opposed locations on said first tubularelement; second diametrically opposed gimbal pin means on said gimbalring, disposed angularly intermediate said first gimbal pin means; saidsecond gimbal pin means pivotally mounting said second tubular elementat two diametrically opposed locations on said second tubular element;and a tubular sealing ring having a through bore and first and secondaxial ends; means defining a coaxial, annular sealing surface on eachend of said sealing ring; said sealing ring being received within saidjoint with said first axial and coaxial, annular sealing surface insealing engagement with the annular, coaxial, concave, sphericallycurved sealing surface of said first tubular element, with said secondaxial end coaxial, annular sealing surface in sealing engagement withthe annular, coaxial, concave, spherically curved sealing surface ofsaid second tubular element, with said through bore thereofcommunicating between the through bores of said first and second tubularelements, and with longitudinal axes of said first and second gimbal pinmeans passing through the geometric center of said sealing ring.

3. The gimbal joint of claim 2 wherein said sealing ring, at least atthe first and second axial ends thereof,

I is made of resilient material, said sealing ring having a .free axiallength between said sealing surfaces thereof greater than the directdistance between corresponding points on said sealing surfaces of saidtubular elements engaged by the sealing ring sealing surfaces, wherebysaid sealing ring sealing surfaces resiliently engage said sealingsurfaces of said tubular elements.

4. The gimbal joint of claim 2, wherein the two tubular elements eachinclude two diametrically opposed ears extending axially beyond said oneend of each; each ear having means defining an opening therethroughradially of the respective tubular element, all on axes passing throughthe geometric center of the sealing ring; means defining fourequiangularly spaced, radially outwardly opening sockets in said sealingring, all on axes passing through the geometric center of the sealingring; said gimbalring circumferentially surrounding all of said ears;said first gimbal pin means passing radially inwardly through respectiveof the openings through the two ears of the first tubular element andinto two diametrically opposed ones of the sockets on said sealing ring;said second gimbal pin mean passing radially inwardly through respectiveof the openings through the two ears of the second tubular element andinto the remaining two diametrically opposed ones of the sockets on saidsealing ring.

5. The gimbal joint of claim 4 wherein said sealing ring through bore,centrally thereof, is at least as large in diameter as the through boresof said first and second tubular elements; said sealing ring throughbore enlarging in diameter from centrally thereof toward both axial endsthereof, whereby a fully open bore is maintained throughout said jointduring gimbaling thereof.

6. The gimbal joint of claim 4 further including two load cells secured,at one end of each, to diametrically opposed points on said firsttubular element angularly intermediate the two cars thereon and secured,at an opposite end of each, to diametrically opposed points on saidgimbal ring; and two load cells secured, at one end of each, todiametrically opposed points on said second tubular element angularlyintermediate the two ears thereon and secured, at an opposite end ofeach, to diametrical- 1y opposed points on said gimbal ring; each saidload cell comprising a resiliently compressible-expansible member havingan unstressed condition intermediate compressed and expanded extremesthereof and constructed and arranged to offer a restorative forceproportional to the displacement of said member from said unstressedcondition, whereby said gimbal joint is predisposed to maintain anaxially aligned condition.

7. The gimbal joint of claim 6, further including end connector meansone each tubular element adjacent the opposite end thereof from thesealing surface thereof, for securely interposing said gimbal joint in astring of conduit.

8. The gimbal joint of claim 4, further including at least one load cellsecured, at one end thereof, to one of said first tubular element,angularly intermediate the two ears thereon, and said gimbal ring andhaving the opposite end thereof positioned to bear against the other ofsaid first tubular element, angularly intermediate the two ears thereonand said gimbal ring; said load cell comprising a resilientlycompressible member constructed and arranged to offer a restorativeforce proportional to the compression of said member as said firsttubular element, angularly intermediate the two ears thereon at thelocation of said load cell is relatively moved toward said gimbal ring,whereby said gimbal joint is predisposed to maintain an axially alignedcondition between said first tubular element and said gimbal ring.

9. The gimbal joint of claim 8, further including at least one load cellsecured at one end thereof to one of said second tubular element,angularly intermediate the two cars thereon, and said gimbal ring andhaving the opposite end thereof positioned to bear against the other ofsaid second tubular element, angularly intermediate the two ears thereonand said gimbal ring; the second mentioned load cell being displacedfrom the first mentioned load cell by about 90 degrees with respect tothe longitudinal axis of the gimbal joint and comprising a resilientlycompressible member constructed and arranged to offer a restorativeforce proportional to the compression of said member as said secondtubular element, angularly intermediate the two ears thereon at thelocation of the second mentioned load cell is relatively moved towardsaid gimbal ring, whereby said gimbal joint is also predisposed tomaintain an axially aligned condition between said second tubularelement and said gimbal ring.

10. A marine riser for providing, during an intermediate stage of welldrilling, communication between a drilling vessel and well controlequipment at an underwater well head comprising: a string of conduithaving connector means at the lower end thereof constructed and arrangedto secure said string of conduit to said well control equipment, andhaving support means at the upper end thereof for connection to thedrilling vessel for supporting at least part of the weight of the stringof conduit from the drilling vessel; and a gimbal joint interposed insaid string of conduit adjacent said connector means, said gimbal jointcomprising: a first tubular element having a longitudinal through bore;a second tubular element having a longitudinal through bore; meansdefining an annular, coaxial, concave, spherically curved sealingsurface on each of said tubular elements, within the through borethereof, adjacent and enlarging toward one end of respective tubularelements; a gimbal ring disposed circumferentially of said jointadjacent said tubular element one ends; first gimbal pin means on saidgimbal ring, proceeding radially thereof from two diametrically opposedlocations on said gimbal ring; said first gimbal pin means pivotallymounting said first tubular element at two diametrically opposedlocations on said first tubular element; second diametrically opposedgimbal pin means on said gimbal ring, disposed angularly intermediatesaid first gimbal pin means; said second gimbal pin means pivotallymounting said second tubular element at two diametrically opposedlocations on said second tubular element; and a tubular sealing ringhaving a through bore and first and second axial ends; means defining acoaxial, annular sealing surface on each end of said sealing ring; saidsealing ring being received within said joint with said first axial endcoaxial, annular sealing surface in sealing engagement with the annular,coaxial, concave, spherically curved sealing surface of said firsttubular element, with said second axial end coaxial, annular sealingsurface in sealing engagement with the annular, coaxial, concave,spherically curved sealing surface of said second tubular element, withsaid through bore thereof communicating between the through bores ofsaid first and second tubular elements, and with longitudinal axes ofsaid first and second gimbal pin means passing through the geometriccenter of said sealing ring; said first and second tubular elementsconstituting part of said string of conduit.

11. A marine riser for providing, during an intermediate stage of welldrilling, communication between a drilling vessel and well controlequipment at an underwater wellhead comprising: a string of conduithaving connector means at the lower end thereof constructed and arrangedto secure said string of conduit to said well control equipment, andhaving support means at the upper end thereof for connection to thedrilling vessel for supporting at least part of the weight of the stringof conduit from the drilling vessel; and a plurality of longitudinallyspaced gimbal joints interposed in said string of conduit atlongitudinally spaced locations therealong, including one adjacent saidconnector means, each of said gimbal joints comprising: a first tubularelement having a longitudinal through bore; a second tubular elementhaving a longitudinal through bore; means defining an annular, coaxial,concave, spherically curved sealing surface on each of said tubularelements, within the through bore thereof, adjacent and enlarging towardone end of respective tubular elements; a gimbal ring disposedcircumferentially of said joint adjacent said tubular ele ment one ends;first gimbal pin means on said gimbal ring, proceeding radially thereoffrom two diametrically opposed locations on said gimbal ring; said firstgimbal pin means pivotally mounting said first tubular element at twodiametrically opposed locations on said first tubular element; seconddiametrically opposed gimbal pin means on said gimbal ring, disposedangularly intermediate said first gimbal pin means; said second gimbalpin means pivotally mounting said second tubular element at twodiametrically opposed locations on said second tubular element; and atubular sealing ring having a through bore and first and second axialends; means defining a coaxial, annular sealing surface on each end ofsaid sealing ring; said sealing ring being received within said jointwith said first axial end coaxial, annular sealing surface in sealingengagement with the annular, coaxial, concave, spherically curvedsealing surface of said first tubular element, with said second axialend coaxial, annular sealing surface in sealing engagement with theannular, coaxial, concave, spherically curved sealing surface of saidsecond tubular element, with said through bore thereof communicatingbetween the through bores of said first and second tubular elements, andwith longitudinal axes of said first and second gimbal pin means passingthrough the geometric center of said sealing ring; the two tubularelements each including two diametrically opposed ears extending axiallybeyond said one end of each; each ear having means defining an openingtherethrough radially of the respective tubular element, all on axespassing through the geometric center of the sealing ring; means definingfour equiangularly spaced, radially outwardly opening sockets in saidsealing ring, all on axes passing through the geometric center of thesealing ring; said gimbal ring circumferentially surrounding all of saidears; said first gimbal pin means passing radially inwardly throughrespective of the openings through the two ears of the first tubularelement and into two diametrically opposed ones of the sockets on saidsealing ring; said second gimbal pin means passing radially inwardlythrough respective of the openings through the two ears of the secondtubular element and into the remaining two diametrically opposed ones ofthe sockets on said sealing ring; and each gimbal joint furtherincluding: two load cells secured, at one end of each, to diametricallyopposed points on said first tubular element angularly intermediate thetwo cars thereon and secured, at an opposite end of each, todiametrically opposed points on said gimbal ring; and two load cellssecured, at one end of each, to diametrically opposed points on saidsecond tubular element angularly intermediate the two ears thereon andsecured, at an opposite end of each, to diametrically opposed points onsaid gimbal ring; each said load cell comprising a resilientlycompressible-expansible member having an unstressed conditionintermediate compressed and expanded extremes thereof and constructedand arranged to offer a restorative force proportional to thedisplacement of said member from said unstressed condition, whereby saidgimbal joint is predisposed to maintain an axially aligned condition;the first and second tubular elements of each gimbal joint constitutingpart of said string of conduit.

12. The marine riser of claim 11 wherein all of the load cellresiliently compressible-expansible members have substantially equalforce constants; and wherein the load cells of each gimbal joint areconstructed and arranged to limit maximum longitudinal axis angulardeflection of the first and second tubular elements thereof, withrespect to one another, of about four degrees.

13. In a tubular joint having a first and a second axially alignablepivotally interconnected tubular conduit elements and including meanssealingly interconnecting the through bores of the two tubular conduitelements, the improvement comprising: a support member positionedadjacent the pivotal interconnection of the tubular conduit elements; atleast one load cell having an end thereof secured to one of the firsttubular conduit element and support member and an opposite end thereofpositioned to bear against the other of said first tubular conduit andsaid support member; said load cell including resiliently compressiblemeans for exerting an axial alignment restoring force between thesupport member and the first tubular conduit element in proportion tothe deflection of the first tubular conduit element from axial alignmentwith the support member.

References Cited UNITED STATES PATENTS 1,681,626 8/1928 Russell 285265 X2,936,185 5/1960 Olsen et al 285265 X 3,142,344 7/1964 Otteman et a1285223 X 3,168,334 2/1965 Johnson 285223 X 3,189,372 6/1965 Johnson166-.5 X 3,433,504 3/1969 Hanes 285264 X ERNEST R. PURSER, PrimaryExaminer R. E. FAVREAU, Assistant Examiner US. Cl. X.R. 285265

